This invention relates generally to closure means for bags and more particularly to a closure means for a tamperproof bag. Tamperproof bags are used in various applications such as, for example, bank deposit bags, police evidence bags, and prescription containing bags in hospitals. Tamperproof bags of the indicated type must provide a secure closure of the bag opening to resist reopening of the bag once it is closed and the closure must be capable of revealing any tampering with or attempts to reopen the bag.
Present-day tamperproof bags are not entirely satisfactory since they are generally too expensive and are not completely tamperproof. For example, one common tamperproof bag in use today comprises a plastic bag closed at one end and have a flap adapted to be folded over an open end. A first adhesive tape is adhered to the inside wall of the flap and a second adhesive tape is adhered to the bag area adjacent the opening. Each of these tapes is provided with a protective liner which must be removed prior to adhering the flap into the closed position. This type of construction is expensive and involves difficult manufacturing techniques in applying the adhesive tapes to the bag.
In accordance with the invention there is provided a novel means for closing a bag of the indicated type. The bag closure of the invention comprises a strip of microcapsules which are applied as a band along an area of the inside surface of a flap and along an area of the outside surface of the end of a bag wall adjacent the bag opening. The microcapsules contain an adhesive core enclosed by a non-adhesive shell adapted to be broken upon the application of pressure thereto to release the adhesive contents which serves to seal the flap onto the bag wall in the bag closing position.
In accordance with the invention there are provided two methods for applying the microcapsules to the appropriate areas of the bag. In accordance with one method a dispersion of the microcapsules in a binder system is coated onto the bag and the binder system is dried to drive off non-active binder ingredients leaving the microcapsules adhering to the bag. In accordance with another method of the invention, an adhesive tie-coat is applied to the bag and the microcapsules are then dusted onto the adhesive, after which excess microcapsules are removed, as by vacuum or another suitable method.